Determination of Dynamic Fracture Toughness at High Loading Rates

2012 ◽  
Author(s):  
Uwe Mayer
Keyword(s):  
Fracture Toughness ◽  
Elastic Waves ◽  
Crack Arrest ◽  
Dynamic Fracture Toughness ◽  
High Loading ◽  
Dynamic Crack ◽  
Testing Time ◽  
Loading Rates ◽  
Propagation Of Elastic Waves

To determine fracture mechanics values at high loading rates from force and displacement signals requires the influences of inertia and the propagation of elastic waves to be taken into account. This paper shows how measurement technique requirements can be fulfilled for determination of key values for a testing time below 100μs for 1T C(T) specimens. Results using this method are given for specimens of 22 NiMoCr 3 7 steel (A 508 C1.2) from a project on correlation between dynamic crack initiation and crack arrest.

Fracture Mechanics at Elevated Loading Rates in the Ductile to Brittle Transition Region

2017 ◽  
Author(s):  
Uwe Mayer ◽  
Thomas Reichert ◽  
Johannes Tlatlik
Keyword(s):  
Fracture Toughness ◽  
Dynamic Loading ◽  
Dynamic Fracture ◽  
Master Curve ◽  
Crack Arrest ◽  
Dynamic Fracture Toughness ◽  
Fracture Probability ◽  
High Rate ◽  
Loading Rates ◽  
Static Conditions

The rate-dependent reference temperature T0,x characterizes the fracture toughness of ferritic steels at the onset of cleavage. Fracture toughness values KJc,d were determined according to the Annex A1 of ASTM E1921 [1] which refers to the high rate annexes A14 and A17 of ASTM E1820 [2]. Results of extensive dynamic fracture toughness experiments at various loading rates, temperatures, specimen types and sizes revealed shortcomings in the transferability of the shape of the Master Curve under quasi-static conditions to elevated loading rates. In particular, the quasi-static Master Curve predicts lower fracture toughness values towards higher temperatures than experimentally observed under dynamic loading causing a steeper Master Curve shape. Fractographic examinations proved the relevance of local crack arrest under dynamic loading conditions, which is consistent with the view of the parallelism of dynamic fracture probability and probability of arrest.

IAEA Coordinated Research Project on Master Curve Approach to Monitor Fracture Toughness of RPV Steels: Effect of Loading Rate

2007 ◽  
Author(s):  
Hans-Werner Viehrig ◽  
Enrico Lucon
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Loading Rate ◽  
Crack Arrest ◽  
Dynamic Fracture Toughness ◽  
Current Status ◽  
Research Project ◽  
Topic Area ◽  
Loading Rates ◽  
Data Assessment

In the final evaluation for the application of the Master Curve in the IAEA Coordinated Research Project Phase 5 (CRP-5), one of the areas which was identified as needing further work concerned the effects of loading rate on the reference temperature To up to impact loading conditions. This subject represents one of the three topic areas within the current CRP-8. The effect of loading rate can be broken down into two distinct aspects: 1) the effect of loading rate on the Master Curve To values for loading rates within the specified in ASTM E1921-05 for quasi-static loading (0.1–2 MPa√m/s); 2) the effect of loading rate on To values for higher loading rates, including impact conditions using instrumented precracked Charpy (PCC) specimens. The new CRP includes both aspects, but primarily focuses on the second element of loading rate effects, i.e. loading rates above 2 MPa√m/s. These issues are investigated within the topic area #2 of CRP-8 (Loading Rate Effect). The mandatory portion of this topic area required participation in a round-robin exercise (RRE) to validate the application of the Master Curve approach to PCC specimens tested in the ductile-to-brittle transition region using an instrumented pendulum (10 tests per participant on the JRQ material). The current status of the RRE is presented in [1]. The non-mandatory portion of this topic area consists in providing Master Curve data obtained at different loading rates on various RPV steels, in order to assess the loading rate dependence of To and compare it with an empirical model proposed by Wallin. Moreover, additional topics will be addressed, such as: • comparison of results from unloading compliance and monotonic loading in the quasi-static range; • estimation of fracture toughness from Charpy V-notch data; • assessment of crack arrest properties from instrumented Charpy results; • effect of irradiation on the relationship between static and dynamic fracture toughness.

Discussion of a New Experimental Method in Measuring Fracture Toughness Initiation at High Loading Rates by Stress Waves

1982 ◽  
Vol 104 (1) ◽  
pp. 29-35 ◽  
Author(s):  
J. R. Klepaczko
Keyword(s):  
Fracture Toughness ◽  
Experimental Method ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Fracture Initiation ◽  
High Loading ◽  
Screening Tests ◽  
Hopkinson Pressure Bar ◽  
Loading Rates ◽  
Wide Range

An experimental method is described for measuring the fracture initiation properties of metals and alloys over a wide range of loading rates, which can cover over six orders of magnitude in K˙I (1 MPam s−1 ≤ K˙I ≤ 106 MPam s−1). With some modification of the standard compact tension specimen, a large series of screening tests can be performed in the high loading region at a relatively low cost. At the lower loading rates a standard closed loop testing machine can be used. To evaluate fracture initiation at a very high loading rate, a special arrangement of the split Hopkinson pressure bar has been proposed. Specimens of the same geometry as those used in quasi-static tests are placed between the Hopkinson bars. Since the wedge is attached to the incident bar, and the specimen is backed by the transmitter bar (Fig. 2), the course of specimen loading and fracturing can be exactly monitored by recording the incident, reflected and transmitted longitudinal waves. Using this technique, fracture initiation of the prefatigued specimen has been achieved within ∼ 20 μs after the beginning of specimen loading. The effects of inertia acting on the specimen and an error introduced by friction are both considered. Experiments performed on some aluminum alloys as well as on medium carbon steel revealed a complicated pattern of the fracture toughness behavior. Generally, for the strain rate sensitive materials a substantial decrease in fracture toughness was observed under high loading rates.

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